1. Field of the Invention
The present invention relates to a control system for a boat having plural propulsion units provided side by side, and more particularly to a control system that selectively synchronizes engine speeds of the respective propulsion units with each other.
2. Description of the Related Art
One conventional boat has three propulsion units, such as outboard motors, stern drives or inboard-outdrive arrangements, provided side by side at its stern. In this type of boat, there typically are provided three shift/throttle lever pairs associated with corresponding ones of the individual propulsion units. Operating the six levers in addition to a steering wheel is cumbersome and can be troublesome to the operator.
To address this issue, one proposed control system connects operation control units for controlling operating conditions of outboard motors to each other via a communication line for sending and receiving information on operations of the respective outboard motors (See Japanese Publication No. JP-A-Hei 8-200110). In addition, another proposed control system uses two adjacent left and right operation levers to control shift and throttle operations of all of the plural propulsion units. With the operation levers tilted at equal angles, if the engines of the left and right propulsion units rotate at different speeds, a motor of a throttle actuating unit is actuated so as to equalize the engine speeds of the left and right propulsion units with respect to the engine speed of the right propulsion unit. As such, the engine speeds of the left and right propulsion units are synchronized with each other automatically (See Japanese Publication No. JP-A-2000-313398).
As described above, with the left and right operation levers tilted at equal angles, the control system synchronizes the engine speeds of the respective propulsion units with each other. However, variations in engine speed, variations in throttle opening or an engine load condition may exist because of, among other things, differences in the engines mounted to the respective propulsion units. These variable conditions occasionally impair the control system from immediately and smoothly synchronizing the engine speeds of the respective propulsion units with each other.